This invention relates to a process and an arrangement for the strengthening of an end portion of a yarn which is produced at a spinning station of a spinning machine comprising a plurality of such spinning stations and which, after the interruption of the spinning operation, extends between a stopped spool package and a suction withdrawal device assigned to the spinning station.
In the case of yarn packages which are produced on a spinning machine, the end portion of a spinning yarn must have a certain strength so that, when used on machines which process it further, it can be processed without any disturbance, particularly without any yarn breakage. Particularly in cases where the feeding and threading of the yarn end portion with respect to the machine for the further processing is to take place by means of automatic devices, it is necessary that the yarn end portion has a particularly high strength along a certain length. This requirement exists particularly when the yarn has received only a slight strength during the spinning. This is likely to occur in the case of such yarns where the two yarn components of the yarn were only prestrengthened and were then wound onto the cross-wound package in side-by-side windings. Although the strength of this yarn will be sufficient for the later twisting, yarn breakages can very easily occur when this prestrengthened yarn is processed on the twisting machine or when it is conveyed to the twisting machine.
From the German Patent Document DE-A 39 09 420, it is known that the end portion of a prestrengthened double yarn which is to be placed on a spool package is strengthened during the formation of the final windings. In this case, the double yarn end to be strengthened is held by a machine-side suction withdrawal device and extends to the spool package which is folded away from its drive. A movably arranged servicing device, which is applied to the corresponding spinning station, is equipped with an auxiliary winding roller by means of which the spool package of the respective spinning station can be driven. By means of the auxiliary winding roller, the yarn end portion which is held by the machine-side suction withdrawal device is pulled out of the latter. The strengthening is provided along a length of 0.5 m in such a manner that the yarn portion to be strengthened during the winding-up is guided through a whirl nozzle which is mounted between the machine-side suction withdrawal device and the yarn package. At the whirl nozzle, a pneumatic twisting takes place of the double yarn which is guided through it.
It is an object of the invention to provide a process and an arrangement by means of which, in a simple manner, a particularly effective strengthening of the end portion of a yarn can be carried out.
With respect to the process, this object is achieved according to preferred embodiments of the invention in that the yarn end projecting into the suction withdrawal device is gripped, is lengthened by winding-of f the yarn wound onto the package, and is then strengthened in an essentially stationary position by means of a twisting entered in the area of the yarn end. As a result of these measures, a sufficiently long strengthened yarn end portion is obtained, on the one hand, and, on the other hand, a particularly effective strengthening is achieved because the yarn end portion receives a true twist because of the free yarn end. The twist, which is entered in the stationary position, contributes to a strengthening that can be carried out in a particularly targeted manner. By means of the corresponding winding-of f of the yarn from the package, the length of the yarn end portion which is to be strengthened can be determined.
In a further development of the invention, it is provided that the yarn end portion to be strengthened is held in a clamped fashion during the strengthening. This results in a particularly effective strengthening.
In a further development of the invention, it is provided that the strengthening takes place by a mechanical twisting of the yarn end portion situated between a clamping element and the package. Mechanical twisting is more effective than, for example, pneumatic twisting and can be carried out with fewer expenditures than other types of strengthening, such as the adding of an auxiliary yarn.
In a further development of the invention, it may be provided that the end portion of the yarn which is not intended to be strengthened is cut off. In this manner, it is possible to strengthen a yarn portion of a defined length irrespective of how much yarn is situated in the machine-side withdrawal pipe.
In a further development of the invention, it is provided that the length of the yarn to be strengthened can be determined by the application point of the twisting. As a result, it becomes possible to vary and precisely determine the length of the yarn portion to be strengthened.
In a further development of the invention, it is provided that the yarn end projecting into the suction withdrawal device is gripped by means of a gripping element; together with a yarn portion wound of f the package, is sucked into a suction pipe assigned to the spinning station; and is then strengthened by a twisting entered in the area of the yarn end. As a result of the vacuum acting inside the suction pipe, first a yarn loop is formed to the yarn end portion extending into the withdrawal pipe. When a sufficiently large loop has been sucked into the suction pipe, the gripping element is released so that now yarn wound off the package is taken in. The yarn portion sucked into the suction pipe can then be cut, in which case particularly the yarn portion which previously had projected into the machine-side withdrawal pipe is removed. Finally, the yarn portion extending between a clamping element and the package is strengthened in that the twisting is entered in the area of the yarn end. Thus, the yarn end portion receives a true twist. Since the yarn portion to be strengthened is housed completely in the suction pipe, it is easily possible to strengthen an arbitrary length of yarn without any catching of the yarn portion anywhere.
In the case of a preferred embodiment of an arrangement for carrying out the process, each spinning station of the spinning machine is provided with a withdrawal pipe connected behind a withdrawal device in the yarn travelling direction. Devices for uncoupling the drive are provided on the package receiving the spun yarn. Furthermore, the arrangement has a controllable gripping element which can be applied to the yarn projecting into the withdrawal pipe. By means of the gripping element, the yarn can be guided away from the withdrawal pipe. Furthermore, a twisting device is provided by means of which the yarn end portion leading onto the package can be strengthened by means of a twisting entered in the area of the yarn end. By means of an arrangement of this type, the yarn end portion can be provided with a true twist.
In a further development, it is provided that the twisting device is constructed with a clamping element for the yarn to be strengthened. By means of such a clamping element, the yarn is clamped and, during the strengthening, is situated in an essentially stationary position.
In a further development of the invention, it may be provided that the gripping element and the twisting device are assigned to a servicing arrangement which is movably arranged on the spinning machine and can be selectively applied to the spinning stations. On such movable servicing arrangements, which are known in principle, additional devices may be arranged for carrying out servicing operations. In particular, devices for eliminating a yarn breakage should be mentioned here.
In a further development of the invention, it may be provided that the gripping element and the twisting device are arranged on a common swivel arm which can be applied to the spinning station. The swivel arm, which is arranged on the servicing arrangement, is coupled with a controllable drive. During the travelling movement of the servicing arrangement, the swivel arm is situated inside the servicing arrangement. In the operating Position, the swivel arm is swivelled out of the servicing arrangement. The yarn end is gripped by the gripping element and is guided away from the intake device. The desirable length of the strengthened area can be varied by the swivel position of the swivel arm.
In a further development of the invention, it may be provided that a cutting device is assigned to the twisting device by means of which the end portion of the yarn which is not to be strengthened can be cut off.
In an advantageous embodiment of the invention, a suction pipe is provided which is assigned to the servicing arrangement, can be applied to the withdrawal pipe and, on its mouth opening facing away from the servicing arrangement, is provided with a yarn clamp and, on its opposite opening, is provided with a twisting device. The devices operate in that the yarn clamp constructed as a gripping element first grips the yarn portion in the area of the machine-side withdrawal pipe, in which case it is sucked into the applied suction pipe while forming a loop. As soon as the vacuum existing in the applied suction pipe is sufficiently large, the yarn clamp will release the yarn portion. In this case, another yarn portion, which had been wound off from the package by means of an auxiliary winding roller, is taken in. The yarn portion will then be cut off at a predetermined length and is twisted in the clamped condition. It may also be provided that the cutting device and the twisting device are arranged inside the suction pipe at some distance from its mouth opening. The twisting device may also be arranged such that it is situated at the end of the yarn portion to be twisted. It is also contemplated, however, to let the end of the yarn portion to be twisted enter farther into the suction pipe so that the length of the yarn portion to be twisted can be varied. The length of the yarn portion to be strengthened can be varied by the point of application of the twisting device. This point of application can be changed by the arrangement of the twisting device in the suction pipe, by changing the length of the suction pipe or by swivelling the suction pipe.
In the case of an advantageous further development, it is provided that the twisting device is designed as a rotatably driven tube into which the yarn to be strengthened can be introduced and to which a clamping element is assigned which can fix the yarn.
In an advantageous further development, two clamping devices are provided as the clamping element which can be introduced into the interior of-the tube and can be brought to rest against one another. In this case, the yarn portion to be twisted is brought, for example, sucked, into the interior of the tube. By means of the subsequently entered rotating movement of the tube, the yarn is clamped in by means of the clamping elements and is strengthened at the same time by providing the yarn end portion with a true twist.
It is also possible to establish the contact position of the clamping elements by means of a solenoid acting outside the tube.
In a further development of the invention, it is provided that the clamping elements are developed as wing-type double levers which are received in mutually opposite recesses of the tube and are pivotally arranged on pins in the recesses. The arrangement of the pins takes place in such a manner that a shorter and a longer leg respectively are formed on the double lever. Because of the centrifugal force which occurs when the tube is rotated, the longer legs are moved toward the outside and the shorter legs are therefore moved toward the inside. In this case, the yarn introduced into the pipe is clamped between the shorter legs.
In this case, it may advantageously be provided that the tube has a rectangular cross-section in the area in which the double levers are arranged.
It may also advantageously be provided that the double levers in their inoperative position completely fill the recesses of the tube. In the case of this construction, secondary air is avoided which could impair the suction effect of the tube with respect to the yarn. In the inoperative position of the twisting device, the suction air can flow freely through the clamping element without any impairment.
A particularly simple construction of the arrangement is achieved in that the clamping element of the twisting device is at the same time constructed as a gripping element. In the case of this development, the clamping element must be operable from the outside. The operating may expediently take place in an electromagnetic manner.
In the case of another advantageous development, the twisting device has a rotatably arranged drivable slotted disk with a radially arranged slot which extends to the center. The yarn to be strengthened can be inserted into this slot and can be fixed by means of a yarn clamp arranged on the slotted disk. The yarn to be strengthened is introduced into the slot up to the center and is held by the yarn clamp which can be operated from the outside. Then the disk is rotated. This twists the yarn portion held by the yarn clamp. Other than in the case of the above-described tube-shaped twisting device, in the case of this construction, the yarn portion to be twisted is introduced from the side, in which case it is also easily possible to apply the twisting device to the yarn. A twisting device of this type is recommended in cases where no additional suction pipe is to be used. The yarn clamp may expediently be operable from the outside by means of a solenoid or by means of mechanical devices. However, it is also contemplated to construct the yarn clamp such that it operates with centrifugal force.
In a further development of the invention, the slotted disk can be rotated by means of an assigned driving disk. The driving disk, which is coupled with a drive, transmits its rotating movement to the slotted disk. This provides the yarn which is introduced into the slot of the slotted disk with a true twist. It is also contemplated to arrange several driving disk on the slotted disk.
In an advantageous development, the slotted disk and the driving disk are magnetically connected with one another. Since a conventional radial bearing cannot be used on the slotted disk, the magnetic connection provided between the driving disk and the slotted disk prevents a lateral moving-away of the slotted disk.
In another advantageous development, the slotted disk can be driven by means of two magnetic driving disks which are applied to its circumference. The slotted disk can be secured against a radial displacement by being arranged between rims.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.